Reading the live spectrum
The curve runs from the lowest frequency on the left to the highest on the right, on a logarithmic scale so each octave gets the same width, the way pitch sounds. Height is level in dBFS per frequency bin. Peaks are tones, a raised slope is noise, and the orange peak-hold line shows the loudest each frequency has been since you switched it on (switch it off and on under Settings to reset it). The scrolling spectrogram under the curve keeps the last few seconds, so a sound that came and went is still there to point at.
Resolution: what the FFT size buys
The analyzer splits the sound into frequency bins. More points mean finer bins but a longer frame of sound per reading, so the display reacts more slowly. At a 48 kHz sample rate:
| FFT size | Bin spacing | Frame length |
|---|---|---|
| 1024 | 46.9 Hz | 21.3 ms |
| 2048 | 23.4 Hz | 42.7 ms |
| 4096 | 11.7 Hz | 85.3 ms |
| 8192 | 5.9 Hz | 170.7 ms |
| 16384 | 2.9 Hz | 341.3 ms |
The page starts at 8192, fine enough to separate two steady tones about 12 Hz (two bins) apart. The resolution line under the settings shows the values for your device’s actual sample rate.
Things to find with it
- Mains hum: a narrow peak at 50 or 60 Hz (the grid frequency where you are) and its multiples, from a ground loop, a cheap power supply or an unshielded cable. Hold the microphone near the suspect device and watch which peaks rise.
- Feedback and ringing: in a PA or a room, a frequency that keeps building up shows as one peak racing above the rest. The note readout tells you where to cut on an equaliser.
- Speaker and headphone checks: play a sweep or steady tones from the tone generator and watch where the level falls off. The microphone’s own response is in the result too, so compare devices with the same microphone.
- Tuning by ear and eye: the readout names the strongest frequency as a note with cents, handy for a rough check of a string, a whistle or a bell.
For channel and polarity checks of speakers, the speaker test plays the right signals.